1. Field of the Invention
The present invention relates to a position-control stage with onboard linear motor, which has been extensively used in machinery including semiconductor and liquid display manufacturing equipment, measuring instruments, assembling machines, tool machines, industrial robots, conveyors and, more particularly, to a position-control stage in which an armature coil is installed in, for example, a stationary bed while a field magnet lies on a turntable.
2. Description of the Prior Art
In recent years, current multi-axis stages and moving mechanisms such as X-Y plotters employed in the diverse technical fields using machinery as stated earlier have required more and more a slider unit, which is made compact or slim in construction and light in weight, and moreover able to operate with high propulsion, high speed and high response to provide high speed travel and precise position control for works, tools, articles and instruments. Linear motors commonly used in the slider units involve two broad types. The first, called moving-coil linear motor has a plurality of moving-armature coils. The second, called moving-magnet linear motor has many moving-field magnets of permanent magnet.
In Japanese Patent Laid-Open No. 2001-352744, there is disclosed a slider unit with onboard moving-magnet linear motor, which is able to move in linear direction. The slider unit is made compact in construction and improved in allowing the slider to travel linearly with high speed and high response relatively to the stationary bed, and thereby helping provide the precise position control of the slider with respect to the stationary bed. In the prior slider unit disclosed in the above citation, the armature assembly is constructed operating on a three-phase current system, and the driving circuit is installed outside the slider unit, instead of inside the slider unit, to make the stationary bed simple in construction and reduced in overall height. The field magnet is made of rare earth magnet, for example neodymium magnet, which is high in flux density to produce the high propulsion to force the table with high velocity. With the prior slider unit stated earlier, the encoder to monitor the table position relatively to the bed is constructed with an optical encoder having therein a linear scale, which is effective in keeping the slider unit low in the occurrence of dust and dirt, thus ensuring clean environment.
Another Japanese Patent Laid-Open No. 99766/1995 disclosed a driver unit constructed in a circular configuration having a preselected curvature. A linear motor built in the driver unit is provided therein with armature windings lying on a flat and circular bed in close relation with one another, each of the armature windings being wound in a form of substantially hollow rectangle, and sheets of field magnet extending with a preselected curvature as a whole underneath a circular table turning relatively to the bed, each of the field magnet sheets having 5 poles arranged to alternate circularly in polarity. Nevertheless, the driver unit constructed as stated earlier, because there is no center of turning inside the driver unit, is tough in arrangement and difficult to use. Moreover, the prior driver unit is not ready for position-control stages because the field magnets should be arranged with large radius of curvatures.
A commutator linear motor is disclosed in Japanese Patent Laid-Open No. 108960/1983, which is comprised of field magnetic poles lying circularly on a substrate pivoted for angular movement, the field magnetic poles being magnetized with unlike N-pole and S-pole in a way alternating circularly in polarity, and armature windings arranged circularly on a printed-circuit board in opposition to the field magnetic poles, the armature windings being wound in a form of sector. With the commutator linear motor stated earlier, both the field magnetic poles and the armature windings have to be made into the same sector or trapezoid that fits precisely with any desired curvature. Thus, the prior construction is hardly suited to every desired radius of curvature.
Another Japanese Patent Laid-Open No. 91710/1993, moreover, disclosed a motor for swinging motion, which is comprised of a stator yoke for field magnet having mounted thereon with four sectors of permanent magnet, and a rotor substrate for armature winding having mounted thereon four sectors of winding, the stator yoke being flanked by rotor substrates with a somewhat air gap remaining between the stator yoke and any of the rotor substrates. Like the prior circular linear motor recited previously, the prior motor for swinging motion constructed as stated earlier is also hardly suited to every desired radius of curvature, because both the field magnets and the armature windings must be made into the same sector of any desired curvature.
A linear motor suited to any curvilinear way is disclosed in Japanese Patent Laid-Open No. 130765/1993, in which the primary side is constituted with concentrated windings which are laid around the teeth of more than one iron core arranged in piles. The concentrated windings fit on a yoke having a desired radius of curvature, and thereby complete any winding set having the core therein. However, this sort of linear motor would become bulky in dimension.
Meanwhile, production systems linked with semiconductors, for example semiconductor manufacturing equipment, measuring instruments, assembling machines, and so on can advance greatly in years and correspondingly makes a growing demand for high-accurate angular position control stage that can operate with high precision, high speed, high propulsion, high response and clean environment, even with made far compact or slim in construction and far inexpensive in production cost, compared with the conventional slider unit.
In Japanese Patent Laid-Open No. 2002-328191, which was filed for a senior invention of the same applicant as in the present application, there is disclosed a stage system with onboard linear motor where the table is allowed to move angularly over just a tiny angle in circular direction. With the senior stage system recited just above, the table is flanked with a linear motor that is arranged in a way extending out of the table in line with a tangent of the table. Tiny angular position control of the table is made by virtue of the linear motor. The prior stage system has been successful, to some extent, in shrinkage and thinning in structure and improvement in response. The stage system is comprised of a first stage lying on a base stage for linear movement in an X-direction relatively to the base stage, a second stage lying on the first stage for linear movement relatively to the first stage in a Y-direction crossing the X-direction, a turning stage supported on the second stage through a rolling-contact bearing, and a linear motor causing the turning stage to move angularly towards any desired position over a tiny angle in circular direction. The linear motor is made up of the primary side of armature windings arranged lengthwise on any one side of the second stage, and a secondary side of a field magnet on which unlike poles a alternate lengthwise in polarity.
Japanese Patent Laid-Open No. 2002-341076, also filed for another senior invention of the same applicant as in the present application discloses a table system with angular position control, which can move precisely an object in circular direction over any tiny angle, even with made reduced in height and compact or slim in construction. With the table system with angular position control disclosed in just above citation, a table supported on a bed for rotation through a crossed-roller bearing can be moved over a tiny angle in circular direction with a driving means through an arm extending radially from the table. A nut and screw set causes a linear motion that is in line with a tangent of the table, and the linear motion is translated into a circular motion to turn the table in any circular direction by virtue of a combination of a first linear motion guide unit interposed between the bed and a carriage to control the linear motion in the tangential direction, a bearing means interposed between the carriage and a turret means, and a second linear motion guide unit to control a linear motion in the direction that looks towards the center of the table. Nevertheless, the table system with angular position control constructed as stated earlier, because of having no onboard linear motor, could not be made less in height by any means. Thus, problems are parts or components are complicated in construction and position control lacks for precision.
Thus, it remains a major challenge to provide a slider unit advancing in conduction system for armature windings, selection of material for field magnet and fixture construction of sensor cords to make the slider unit less in weight, compact and simple in construction, far more precise in position control of the table relatively to the bed, large in angle allowed for angular movement in circular direction upon position control, reduced in height as low as possible, and inexpensive in production cost.